If you have a binary file format (or packet format) which is described as a C structure, are there any programs which will parse the structure and turn it into neat documentation on your protocol?
The struct would of course contain arrays, other structures, etc., as necessary to describe the format. The documentation would probably need to include things like packing, endianness, etc.
Doxygen is a commonly-used documentation generator. However, if you want to get useful documentation, you'll probably have to mark up your structure definitions with doc comments.
Maybe you should think about this a different way.
"Can I create a documentation format for my packet for which I can generate a C struct?"
Consider for example using XML to define the packet structure and add elements for comments and so forth. It wil be fairly easy to write a simple program that transformed it into an actual C structure
as JaredPar says, an alternate phrasing of this question is:
"What is a good method for describing binary structures?
e.g. something like ABNF but capable of doing bit-packing, endianness, etc.
preferably there would be existing tools to generate not just documentation, but C headers, unpack or struct patterns, and validation tools based on the description"
Of course, if such a thing existed, it would be used to write protocol dissectors for WireShark - the fact that each dissector is implemented in C code implies that it's difficult to express binary formats in a generic way
If you know perl you can try playing with Jeeves:
https://www.rodhughes.com/perl/advprog/examples/Jeeves/
(This source is there; I assume it's all right to use. ;) )
I'm trying to work out something similar to what you need: a parser for structured binary data. I'm looking to Jeeves to output parsing classes in C++ from a meta format. The default parser for Jeeves allows for adding additional tags to each member of a class definition. This would let you automatically include information about endianness, alignment, etc. in comments within your classes (and, of course, implement them in your code).